You can smell the fear in Hollywood. Even the most flawless specimens of surgical perfection are worrying themselves into permanent panic attacks, their every conscious second consumed with doubts about whether they're young enough, rich enough, thin enough or popular enough. The majority of these fears could, in the past, have been assuaged by hugely remunerated therapists and the constant, soothing presence of a retinue of enablers. But, for a certain breed of celebrity, a new fear has come into being, one that can't easily be cured with a kind word or a cleansing chant. More than a disappointing weekend at the box office, more than being omitted from the guest list of the current hot spot, more than being punk'd or papped, young Hollywood fears Perez Hilton.

"Do you know how many times I've fantasised about killing you?" said Jesse Metcalfe, the former Desperate Housewives pin-up, after a chance encounter with the online gossip columnist who had devoted a few posts to speculation about his sexuality. Metcalfe got off easy. In less than two years, more than 2 million regular visitors to perezhilton.com have had the tedium of their work or schooldays alleviated by the self-styled gossip gangsta. They lap up his cheerfully vicious mockery of personalities in decline (specifically the perennially hungover Tara Reid), his randomly selected grudges against hapless stars (specifically Kirsten Dunst and Lindsay Lohan or, as he refers to them, Kiki Drunkst and Lindsay Blohan) and - his trademark - the photo-agency pictures digitally defaced with scribbles of cocaine dribbling out of celebrity noses.

For regular visitors, his frequent almost-as-it-happens postings on events of earth-shattering importance (specifically, Britney and Kevin or, as he refers to the ex, K-Fag) render the weekly gossip tabloids instantly archaic. But it's his ceaseless pursuit of closeted celebs that has made the name Perez Hilton synonymous with the kind of influence and revulsion unseen since the 1940s heyday of legendary venom-dripping gossip columnists Hedda Hopper and Louella Parsons. Countless columns packed with subtle insinuations and pictures with "I'm gay" scribbled over them contributed towards propelling former 'N Sync puppet Lance Bass and ex-Doogie Howser star Neil Patrick Harris on to the cover of People magazine with earnest admissions of their sexuality.

You might imagine that someone so skilled at promoting hate and fear among the C-list would live a shadowy existence. But at around 6.15 every morning, Mario Lavandeira, the beefy, 28-year-old gay Cuban-American who hides behind the pseudonym Perez Hilton, sets up his laptop on a table outside the Coffee Bean & Tea Leaf on the corner of Sunset Boulevard and Fairfax Avenue. Until 9.30 at night, when the club-hopping and whisper-gathering begins, he downs endless coffees and fires off endless malice-tinged posts.

Naturally, a life dedicated as much to building up a personal brand as bringing down the vain, venal and deluded results in a healthy amount of self-regard. Ask him why, among the millions of bitchy bloggers recycling Reese & Ryan breakup stories, he's achieved prominence, he is almost incredulous. "Why me? Because no one does it like me. There's only one me. The website is me. It's a reflection of my personality and my interests. It's the perfect marriage of my skills and experiences. I'm obsessed with pop culture and celebrity. I used to be an actor, I used to be a journalist and I used to be a publicist. I know how all these people think." He's even more incredulous when asked if he ever feels regret for anyone he might have wounded. "Not a single time. Not even when I put up the pictures of Princess Diana as she was dying. I didn't put it on my main page. I said, 'Click here to see the pictures', and even then people were outraged. But they made a choice to see those pictures and then they had the balls to fucking criticise me for it. If I was the kind to have regrets, I wouldn't be doing what I'm doing."

The same goes for those he outs against their will. I bring up the case of Neil Patrick Harris, the rare case of a child star enjoying a second wind. Harris appears in the successful sitcom How I Met Your Mother, playing a smirking womaniser. Doesn't being pushed into admitting he's gay midway through the series kill the credibility of his character? "If anything, it's going to help his career. It already has. There's a false concept that being gay and out in Hollywood will hurt your career. It's intrinsic homophobia. It's as if being gay is bad. The only responsibility I have is to the truth. I wouldn't have said Doogie Howser is gay if I didn't know his boyfriend personally." But isn't it his choice to reveal what he wants about himself? "No, it's not. If a reporter asks [someone like] you whether you're gay or not, it's your choice not to want to talk about your personal life. But if you're a celebrity, you need to be prepared to have the public talk about you because you're making a choice to be in the public arena. I'm just talking about them like I would with any of my friends. It just so happens that I have 2.5 million friends a day come visit me." (In an almost biblical coda, Perez's attempt to extend his brand into a TV pilot was rejected by VH1 because the cable station's bosses were uncomfortable with his targeting celebs for potential outing.)

But perezhilton.com is not just a morass of bitchery and photos of Kelly Preston and Penélope Cruz with digital beards scrawled over their lovely faces. Perez won't hear a word against either his semi-namesake, Paris Hilton, in whose entourage he plays the occasional role of court jester, or the UK. A frequent visitor, he peppers his site with YouTubes of Leona on The X Factor and Shirley Bassey's M&S ad. He's happy to expound on the two nations' differing attitudes towards celebrity: "Like, in the UK, Jordan is a bigger star than Keira Knightley and I love that. The British like their stars to be real and accessible and have flaws and the media talks about them that way, showing all their imperfections, whereas Hollywood wants the stars to be beautiful and not to be fat." The anglophilia continues when Perez seizes on EastEnders and Hollyoaks as useful comparisons with his website: "There are some heroes and some villains. It keeps it exciting and entertaining because you pick up Us Weekly or People and they're talking about the same five people over and over again. I get to write about the freaks, the A-listers, the B-listers, the people who aren't even on the list."

With so many potential victims, how does he zero in on fresh prey? "It's instinctual, it's a gut thing. Sometimes you just don't like a person. I just have this sixth sense to be able to grasp the essence of people and then share that with the world."

A frequent receptacle for Perez's bile is Jennifer Aniston, whom he refers to as Maniston. Now, to me, hating Aniston is like hating a spoon but, when I ask him why he wastes his spleen on someone so bland, he gets full of himself. "Someone else asked me that today. I'll read you my response and then hopefully people will stop asking me that question." He scrolls down his computer and begins to quote himself: "We get asked about our hateration for Maniston a lot and, in this interview, we answer the question quite nicely. Interviewer: What is your problem with her? Perez: I just don't think she's a nice person. I think she doesn't have a sense of humour. I think she's marginally talented, adequately good-looking, doesn't do anything to make the world a better place ..."

Midway through Perez's drawling litany of Aniston's crimes against humanity, I have to step in. That could be a description of anyone I know - barely a reason to hate her. He continues, now with added emphasis on every character flaw: "She just sits all day smoking weed, takes herself way too seriously, is unappreciative of her fans and the media who made her successful and is just pretty much repulsive."

I'm not donning a Team Aniston T-shirt but I'm unmoved. The only point he makes that might have any validity is being unappreciative of her fans. "Very unappreciative," he snaps. "The people that last, the Tom Hankses, the Julia Robertses, my friend John Stamos, are the ones that are nice." I can't let that pass. What about Madonna - who's more horrible and unappreciative of her fans than her? Perez looks as if his head is about to explode. "Madonna's insanely talented!" But you said the people who last are the nice ones. Seeing that my head is now about to explode, he jumps in: "I think Madonna has a sense of humour about herself."

It's almost endearing that this scourge of the C-list celeb who has Hollywood trembling is still so starstruck that he can come out with such a clueless statement. Aware of his faux pas, he retreats into a sulky mumble: "Whatever, it's a gut thing. I don't really like her and I don't have to explain myself." He then goes on for another 10 minutes, listing more reasons why he hates Aniston. None of them holds up.

There's tension between us. Then he gets a message on his laptop and is transported with squealing delight. "Somebody just told me I was on VH1." This was before VH1 rejected his pilot. "They called me an asshole for outing people! I love it. I don't care if they're talking shit about me or praising me, as long as they're talking about me. I love it!"

His cackle echoes across the streets of Hollywood, sending a chill down the spines of passing celebrities ·